A foundational summary dataset for "Persistent warm water anomalies before and after marine heatwaves amplify heat exposure and associated risks"

Utzig Nardi, Ricardo; Fernandes Mazzini, Piero Luigi; Walter, Ryan; Shen, Jian

Publication

A foundational summary dataset for "Persistent warm water anomalies before and after marine heatwaves amplify heat exposure and associated risks"

Utzig Nardi, Ricardo
;
Fernandes Mazzini, Piero Luigi
;
Walter, Ryan
;
Shen, Jian

Abstract

Marine heatwaves (MHWs) are a major threat to marine ecosystems globally, yet standard MHW definitions, despite providing consistent metrics, do not capture pre- and post-event warm anomalies, leading to systematic underestimation of total heat exposure experienced by marine ecosystems. Here, we analyze over 2,580 MHW events from 54 stations across 20 US estuaries to provide a comprehensive characterization of pre- and post-MHW thermal anomalies. We show that pre- and post-event phases are largely independent of core MHW metrics and often persist longer than the MHW itself. Although these phases are less intense than the MHW event, when combined with the MHW itself, they account for a substantial increase in total heat exposure—resulting in an approximately 153% higher cumulative intensity (°C·days) compared to the MHW alone—that cannot be reliably inferred from standard metrics. We present a new framework to quantify pre- and post-event anomalies that can be broadly applied across coastal and open-ocean systems. This framework is critical for understanding MHWs, assessing ecological impacts, guiding laboratory experiments, and informing ecosystem management.

Description

This dataset provides a foundational summary of seasonal baseline climatology and marine heatwave (MHW) metrics spanning pre-, during-, and post-event phases across stations within the National Estuarine Research Reserve System (NERRS; https://coast.noaa.gov/nerrs/). The dataset includes 54 stations distributed across 20 reserves along the U.S. East and West Coasts, Gulf of Mexico, Alaska, and Puerto Rico. Columns include reserve code and station IDs (https://www.nerrsdata.org/dges/ ; see Nardi et al., 2025 https://doi.org/10.1038/s41598-025-91864-6 for further details), seasonal climatological and MHW characteristics, including duration (days), mean intensity (°C), maximum intensity (°C), cumulative intensity (°C·days), rates of onset and decline (absolute values; °C·day⁻¹), and recovery time (days). All metrics are reported as medians together with their corresponding interquartile ranges (25th and 75th percentiles). The dataset enables researchers to incorporate estuary-specific thermal conditions and MHW characteristics into experimental design and comparative analyses. Variables: Seasonal baseline climatology and marine heatwave (MHW) metrics spanning pre-, during-, and post-event phases. Variables include estuarine reserve code, station ID, climatology (°C), duration (days), mean intensity (°C), maximum intensity (°C), cumulative intensity (°C·days), rates of onset and decline (absolute values; °C·day⁻¹), and recovery time (days). All metrics are reported as medians with their corresponding interquartile ranges (25th–75th percentiles). File Format & Software Requirements: The file is provided in Excel (.xlsx) format and can be opened using standard spreadsheet software and common data analysis environments. Dataset Size: 57KB Dataset Time Frame: 1995-2023